Numerical Controller Lookahead Margin for Stable Axis Speed
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Solution Overview
Problem
Numerical controllers experience axis speed fluctuations due to varying lookahead distances, leading to uneven machining surfaces and degraded quality, especially when controlling multiple axes with high processing loads.
Innovation Solution
A numerical controller that sets a target speed based on lookahead distance, decelerating or accelerating as necessary, and maintains this speed within a predetermined margin to minimize fluctuations, using a lookahead unit, analysis unit, target speed calculation unit, interpolation unit, and servo control unit to generate and execute motion instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the numerical controller performs speed control based on varying lookahead distances, then the axis can adapt to different motion requirements, but the axis speed fluctuates causing uneven machined surfaces
Solution Approach 1:
The patent implements dynamic speed adjustment by introducing a margin-based threshold mechanism. When the lookahead distance changes exceed the predetermined margin, the target speed is recalculated; otherwise, the current speed is maintained. This dynamic approach allows the system to adapt to significant motion changes while filtering out minor fluctuations that would otherwise degrade surface quality.
Solution Approach 2:
The patent changes the control parameter from continuous speed adjustment to discrete speed recalculation based on margin thresholds. By monitoring whether lookahead distance changes exceed the margin and only recalculating target speed when necessary, the system transforms continuous parameter variation into discrete parameter changes, thereby reducing speed fluctuations and improving machined surface quality.
2Speed
If the numerical controller frequently recalculates target speed in response to small lookahead distance changes, then the speed control responds quickly to motion changes, but the axis speed fluctuates with small steps
Solution Approach 1:
The patent applies beforehand cushioning by establishing a predetermined margin as a buffer zone before speed recalculation is triggered. This margin acts as a cushion that absorbs small variations in lookahead distance, preventing unnecessary speed recalculations and the resulting speed fluctuations. Only when changes exceed this cushioning margin does the system respond by recalculating target speed.
Solution Approach 2:
The patent implements partial action by selectively recalculating target speed only when necessary - specifically when lookahead distance changes exceed the predetermined margin. This partial recalculation approach avoids excessive speed adjustments for minor changes, thereby maintaining speed stability while still responding to significant motion requirements.
Data Source
AI summary
A numerical controller suppresses change of a axis speed to be slow even when a lookahead distance varies with small steps. The numerical controller includes: a lookahead unit that looks ahead a plurality of instruction blocks from an NC program; an analysis unit that analyzes the looked ahead instruction blocks and creates motion instruction data; a target speed calculation unit that calculates a target speed of the axis based on a lookahead distance; an interpolation unit that generates interpolation data based on the motion instruction data and the target speed; and a servo control unit that controls a motor based on the interpolation data. The target speed calculation unit refrains from recalculation of the target speed when a change of the lookahead distance is within a margin.